Chemistry of proposed calcination/dissolution processing of Hanford Site tank wastes

Technical Report · Sun Jan 01 04:00:00 EST 1995

DOI:https://doi.org/10.2172/10114203· OSTI ID:10114203

Delegard, C H

Plans exist to separate radioactive waste stored in underground tanks at the US Department of Energy`s Hanford Site in south central Washington State into low-level and high-level fractions, and to immobilize the separate fractions in high-integrity vitrified forms for long-term disposal. Calcination with water dissolution has been proposed as a possible treatment for achieving low/high-level separation. Chemistry development activities conducted since 1992 with simulated and genuine tank waste show that calcination/dissolution destroys organic carbon and converts nitrate and nitrite to hydroxide and benign offgases. The process also dissolves significant quantities of bulk chemicals (aluminum, chromium, and phosphate), allowing their redistribution from the high-level to the low-level fraction. Present studies of the chemistry of calcination/dissolution processing of genuine wastes, conducted in the period October 1993 to September 1994, show the importance of sodium fluoride phosphate double salt in controlling phosphate dissolution. Peptization of waste solids is of concern if extensive washing occurs. Strongly oxidizing conditions imposed by calcination reactions were found to convert transition metals to soluble anions in the order chromate > manganate > > ferrate. In analogy with manganese behavior, plutonium dissolution, presumably by oxidation to more soluble anionic species, also occurs by calcination/dissolution. Methods to remove plutonium from the product low-level solution stream must be developed.

• Research Organization: Westinghouse Hanford Co., Richland, WA (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: AC06-87RL10930
• OSTI ID: 10114203
• Report Number(s): WHC-EP--0832; ON: DE95005982; BR: 35AF11201/35AF11202
• Country of Publication: United States
• Language: English

Related Subjects

052001
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
CALCINATION
CHEMICAL COMPOSITION
CHEMICAL REACTION KINETICS
DISSOLUTION
EXPERIMENTAL DATA
HANFORD RESERVATION
HIGH-LEVEL RADIOACTIVE WASTES
LOW-LEVEL RADIOACTIVE WASTES
METALS
NITRATES
NITRITES
RADIOACTIVE WASTE PROCESSING
RADIOACTIVE WASTES
SEPARATION PROCESSES
SODIUM HYDROXIDES
URANIUM
WASTE PROCESSING